Kim Eun Young, Rachubik Patrycja, Dryer Stuart E
Department of Biology and Biochemistry, University of Houston, Houston, TX 77204, USA.
Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, 02-106 Gdansk, Poland.
Cells. 2024 Dec 30;14(1):22. doi: 10.3390/cells14010022.
Podocytes express large-conductance Ca-activated K channels (BK channels) and at least two different pore-forming KCa1.1 subunit C-terminal splice variants, known as VEDEC and EMVYR, along with auxiliary β and γ subunits. Podocyte KCa1.1 subunits interact directly with TRPC6 channels and BK channels become active in response to Ca influx through TRPC6. Here, we confirmed that Ca influx through TRPC channels is reduced following the blockade of BK channels by paxilline. The overall abundance of KCa1.1 subunits, as well as that of β4 and γ3 subunits, were increased in glomeruli isolated from Sprague Dawley rats during chronic puromycin aminonucleoside (PAN) nephrosis. Exposing cultured mouse podocytes for 24 h to recombinant TNFα, a circulating factor implicated in pediatric nephrotic syndromes, did not affect the total abundance of KCa1.1, but did evoke significant increases in both β4 and γ3. However, TNFα evoked a marked increase in the surface abundance of KCa1.1 subunits, similar to that of its previously reported effects on TRPC6 channels. The effect of TNFα on the surface expression of KCa1.1 was eliminated following siRNA knockdown of the β4 subunits, suggesting a role for this subunit in KCa1.1 trafficking to the cell surface. By contrast, treating podocytes with suPAR did not affect the total or surface expression of KCa1.1. The coordinated activation of KCa1.1 channels may promote Ca influx through TRPC channels during normal and abnormal podocyte function by maintaining a membrane potential that allows for the efficient permeation of divalent cations through TRPC pores.
足细胞表达大电导钙激活钾通道（BK通道）以及至少两种不同的形成孔道的KCa1.1亚基C末端剪接变体，即VEDEC和EMVYR，同时还表达辅助性β和γ亚基。足细胞KCa1.1亚基直接与TRPC6通道相互作用，并且BK通道会响应通过TRPC6的钙内流而激活。在此，我们证实，在使用鬼笔环肽阻断BK通道后，通过TRPC通道的钙内流减少。在慢性嘌呤霉素氨基核苷（PAN）肾病期间，从Sprague Dawley大鼠分离的肾小球中，KCa1.1亚基以及β4和γ3亚基的总体丰度均增加。将培养的小鼠足细胞暴露于重组TNFα（一种与小儿肾病综合征有关的循环因子）24小时，并未影响KCa1.1的总丰度，但确实引起β4和γ3均显著增加。然而，TNFα引起KCa1.1亚基表面丰度显著增加，类似于其先前报道的对TRPC6通道的作用。在β4亚基的siRNA敲低后，TNFα对KCa1.1表面表达的作用被消除，表明该亚基在KCa1.1转运至细胞表面中起作用。相比之下，用suPAR处理足细胞并不影响KCa1.1的总表达或表面表达。在正常和异常足细胞功能期间，KCa1.1通道的协同激活可能通过维持允许二价阳离子通过TRPC孔有效渗透的膜电位来促进通过TRPC通道的钙内流。
